Theia: Faint objects in motion or the new astrometry frontier

TL;DR

Theia is a proposed satellite mission aiming for ultra-precise relative astrometry to study faint objects, dark matter, exoplanets, and compact objects, with a novel metrology system achieving sub micro-arcsecond accuracy.

Contribution

It introduces a new satellite concept with extreme astrometric precision and a unique metrology system, surpassing Gaia's accuracy for faint objects.

Findings

Achieves sub micro-arcsecond astrometric precision.

Improves accuracy by a factor of 10-30 for faint stars.

Proposes a versatile mission with open observatory capabilities.

Abstract

In the context of the ESA M5 (medium mission) call we proposed a new satellite mission, Theia, based on relative astrometry and extreme precision to study the motion of very faint objects in the Universe. Theia is primarily designed to study the local dark matter properties, the existence of Earth-like exoplanets in our nearest star systems and the physics of compact objects. Furthermore, about 15 $\%$ of the mission time was dedicated to an open observatory for the wider community to propose complementary science cases. With its unique metrology system and "point and stare" strategy, Theia's precision would have reached the sub micro-arcsecond level. This is about 1000 times better than ESA/Gaia's accuracy for the brightest objects and represents a factor 10-30 improvement for the faintest stars (depending on the exact observational program). In the version submitted to ESA, we proposed an optical (350-1000nm) on-axis TMA telescope. Due to ESA Technology readiness level, the camera's focal plane would have been made of CCD detectors but we anticipated an upgrade with CMOS detectors. Photometric measurements would have been performed during slew time and stabilisation phases needed for reaching the required astrometric precision.